#define  _CRT_SECURE_NO_WARNINGS 1

#include <math.h>
#include <stdio.h>

int main()
{
	float i = 0;
	float f = 0;
	for (i = 1; i <= 100; i++)
	{
		f += pow(-1,((double)i-1)) * (1 / i);
	}
	printf("%f\n",f);

	return 0;
}